利用内容可寻址技术的存储器BISR方法

Memory BISR Based on Content Addressable Memory

随着缺陷密度的增加,在存储器中设计冗余行或冗余列替换有缺陷的存储器单元已成为提高存储器成品率的常用方法.然而基于冗余行或冗余列的修复方法不仅对冗余资源的利用率较低、冗余分析算法较复杂,且受限于存储器生产厂商提供的冗余资源结构.针对此,提出了利用内容可寻址技术结合冗余行和冗余列来修复存储器的方法.该方法中,内容可寻址存储器不仅用于存储修复信息,还被用于当作冗余字替换故障字实现字修复,而冗余行和冗余列则分别用于修复行或列地址译码故障;并在译码逻辑输出端设计控制电路,避免对已修复的故障字进行访问.文中方法简单易行、面积开销小、利于扩展且修复效果好.实验结果表明,该方法在获得同样修复效率的情况下,冗余资源和内容可寻址存储器面积开销最小约为已有二维冗余修复方法的20%.

With increasing defect density, the number of defective cells would be increase. Adding spare rows or columns in memories to replace defective cells is a widely accepted method for yield enhancement. However, existing repair schemes not only have low resource utilization, complex redundancy analysis algorithms, but also greatly depend on the spare structure provided by memory manufactures. Therefore, a repair method using content addressable memory combined with spare rows and columns are proposed in this work. Content addressable memory is not only used to store repair information, but also used as spare words to replace defective words. Meanwhile, spare rows and columns are used to repair row or column address decode defects. A control circuit which controls the access to defective cells is inserted at the output of the address decoder. Advantages of the proposed method are simple implementation, low area overhead, good scalability and high repair rate. Experimental results indicate that the redundancy and content addressable memory area overhead of the proposed repair method is only 20% of other 2D repair methods to obtain the same repair ratio.